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"Switch From Gasoline To Ethanol Linked To Higher Ozone Levels"

"WASHINGTON -- Scientists have made a surprising discovery about ethanol: The more it was used by drivers in Sao Paulo, Brazil, the more ozone they measured in the local environment.

The finding, reported this week in Nature Geoscience, is contrary to other studies predicting that increased use of ethanol would cut levels of ground-level ozone, or smog.

Sao Paulo proved a unique laboratory for studying the effects of ethanol and gasoline usage on local air pollution because 40 percent of the nearly 6 million light-duty vehicles there can run on either fuel. When the percentage of those vehicles using gasoline rose from 14 percent to 76 percent, ambient ozone concentrations in the city fell by about 20 percent, researchers found."